During certain rotating cutting tool operating conditions, vibration or chatter can occur, leading to accelerated tool wear, reduced level of surface finish, and in persistent cases spindle damage. To eliminate or reduce these vibrations without resorting to alternative tooling requires adjustment of the operating parameters, including cutting depth, cutting speed and feed rate, which can very often lead to reduced productivity and efficiency.
The following examples of prior art discuss alternative tooling inventions aimed at reducing/eliminating the negative effects of chatter or vibration whilst maintaining sufficiently high levels of machining efficiency, precision and quality.
U.S. Pat. No. 4,808,044 discloses a face milling cutter, including a cutter body and a plurality of identical cutting inserts detachably mounted in circumferentially spaced pockets formed in the cutter body. First and second recesses are formed in alternate pockets, where the first recess has a bottom facing generally in the direction of rotation and the second recess has a bottom slightly inclined relative to the first recess. Each insert has a generally quadrilateral shape with four main cutting edges formed at the intersection of a front rake face and four side faces, and a flat rear face which interfaces the recess bottom via a support member and is releasably secured by a wedge member. An insert mounted in a pocket with a first recess has a smaller axial rake angle and larger radial rake angle than an insert mounted in an adjacent pocket with a second recess. As a result of different axial and radial rake angles, the inserts in the first and second recesses are subjected to different impact forces on engagement to the workpiece, such that the cutter body is not resonated with the machine tool and chattering is prevented.
U.S. Pat. No. 6,619,891 discloses a milling tool, including a body and at least one set of circumferentially spaced identical cutting inserts detachably mounted on separate seats, where each set includes at least three cutting inserts. Each insert has an active cutting edge situated between a rake surface and a flank surface, where the rake surface faces generally in the direction of rotation and the flank surface faces generally radially outwardly. The seats on the tool body are arranged such that one of the cutting inserts has a clearance angle larger than the clearance angle of at least two other inserts in the same set. This combination results in a milling tool where the larger clearance angle insert generates a smoother surface finish with greater precision and the reduced clearance angle inserts tend to dampen vibrations and provide increased stability.
U.S. Pat. No. 6,997,651 discloses an end mill with a plurality of flutes formed in a cemented carbide cylindrical body, where each flute has an associated peripheral cutting edge and end cutting edge. First and second peripheral cutting edges are alternately arranged as viewed in a circumferential direction of the cylindrical body, as too are corresponding first and second end cutting edges. The first and second peripheral cutting edges have first and second radial rake angles, and the first and second end cutting edges have first and second axial rake angles. The first radial rake angle is larger than the second radial rake angle, and the first axial angle is smaller than the second axial rake angle. This arrangement permits a cutting resistance to be evenly distributed onto all cutting edges of the end mill, thereby preventing chattering.
Each of the prior art inventions discussed above offer different solutions with respect to reducing or preventing chatter by employing a cutting tool with a single geometrical configuration.
It is an object of the present invention to provide an indexable cutting insert which can be used in a rotating cutting tool, specifically a milling cutter, where more than one geometrical configuration can be achieved by indexing at least one of the cutting inserts within the same insert receiving pocket, to offer an alternative solution in reducing vibration and chatter whilst maintaining optimized operating parameters.
It is also an object of the present invention to provide an indexable cutting insert with more than one main cutting edge, where more than one cutter axial rake angle can be achieved by indexing the cutting insert within the same insert receiving pocket of the milling cutter body.
It is another object of the present invention to provide an indexable cutting insert with more than one main rake surface, where more than one cutter radial rake angle can be achieved by indexing the cutting insert within the same insert receiving pocket of the milling cutter body.